Flexible fixation techniques combined with anatomic (open) syndesmosis reduction have demonstrated improved functional outcomes and rates of malreduction. Suture-button devices allow physiologic motion of the syndesmosis without need for implant removal, which may lower the risk of recurrent syndesmotic diastasis. There is limited longer-term assessment of the maintenance of reduction between static and flexible syndesmotic fixation using bilateral ankle CT evaluation.

This is an a priori planned subgroup analysis of a multi-centre, randomized clinical trial comparing static syndesmosis fixation (two 3.5 mm screws) with flexible fixation (single knotless Tightrope) for patients with AO- OTA 44-C injuries. Patients who completed bilateral ankle CT scans at 3- and 12-month follow-up were included. The primary outcome measure was syndesmotic malreduction based on bilateral ankle CT scans, using the uninjured, contralateral ankle as a control. Anterior (ASD), middle (MSD), and posterior (PSD) syndesmosis distance were calculated to measure syndesmosis reduction. Secondary outcomes included re-operation, adverse events and functional outcomes including the EQ5D, Olerud-Molander Ankle Score (OM), Foot and Ankle Disability Index (FADI), and Work Productivity Activity Impairment Questionnaire (WPAI). Paired samples t-tests were used to compare injured to control ankles (R, v 3.5.1).

42 patients (24 Group S, 18 Group T) were included. ASD for Group T was 5.22mm (95%CI 4.69–5.77) at 3 months compared to 4.26mm (95%CI 3.82–4.71; p=0.007) in controls and 5.38mm (95%CI 4.72–6.04) at 12 months compared to 4.44mm (95%CI 3.73–5.16; p=0.048) in controls. ASD for Group S was 4.63mm (95%CI 4.17– 5.10) at 3 months compared to 4.67mm (95%CI 4.24–5.10; p=0.61) in controls, but significantly increased to 5.73mm (95%CI 4.81–6.66) at 12 months compared to 4.65mm (95%CI 4.15–5.15; p=0.04) in controls. MSD results were similar; Group T had a larger MSD than control ankles at 3 months (p=0.03) and 12 months (p=0.01), while the MSD in Group S was not different at 3 months (p=0.80) but increased at 12 months (p=<0.01). 88% (21/24) of Group S had broken or removed screws by 12 months. Unplanned re-operation was 15% in Group S and 4% in Group T (p=0.02), with an overall re-operation rate of 30% in Group S. There was no significant difference between treatment groups for EQ-5D, OM, FADI or WPAI at 3- or 12-month follow-up.

Tightrope fixation resulted in greater diastasis of the ASD and MSD compared to contralateral, uninjured ankles at 3- and 12-months post-fixation. Group S initially had syndesmotic reduction similar to control ankles, but between 3- and 12-months post-fixation, there was significantly increased syndesmosis diastasis compared to controls. The majority of Group S (88%) had either broken screws or scheduled screw removal, which may explain the increased tibio-fibular diastasis seen at 12-months.

Adequate fixation of implant components is an important goal for all arthroplasty procedures. Aseptic loosening is one of the leading causes of revision surgery in total knee arthroplasty. Radiostereometric analysis (RSA) is an imaging technique to measure implant migration, with established migration thresholds for well-fixed, at risk, and unacceptably migrating components. The purpose of the present study was to examine the long-term fixation of a cemented titanium fixed bearing polished tibial baseplate.

Patients enrolled in a previous two-year prospective trial were recalled at ten years. All patients received a cemented, posterior-stabilised total knee replacement of the same design implanted by one of three surgeons. Of the original 35 patients, 16 were available for long-term follow-up, with one patient lost to follow-up, nine patients deceased, and a further nine patients unwilling to return to the clinic. Each patient underwent RSA imaging in a supine position using a conventional RSA protocol. Migration of the tibial component in all planes as well as maximum total point motion (MTPM) was compared between all time points (baseline, six weeks, three months, six months, one year, two years) up to the ten year follow-up visits. Outcome scores including the Knee Society Score (KSS), WOMAC, SF-12, and UCLA Activity Score were recorded.

At ten years, the mean migrations of the tibial component were less than 0.1 mm and 0.1 degree in all planes relative to the post-operative RSA exam. There was no significant difference in tibial component migration between time points. However, MTPM increased significantly over time (p = 0.002), from 0.23 ± 0.18 mm at six weeks to 0.42 ± 0.20 mm at ten years. At one year, 13 patients had an acceptable MTPM level, three patients had an ‘at risk’ level, and no patient had an ‘unacceptable’ level. No patients were revised at ten years. WOMAC and KSS were significantly improved (p < 0.0001) at the latest follow-up compared to pre-operatively, but there was no difference in SF-12. The median UCLA Activity Score at latest follow-up was six (range, two to eight).

The tibial baseplate demonstrated solid fixation at ten years. No patients had an unacceptable MTPM level at one year and no patients were revised at ten years, supporting the use of RSA to predict long-term loosening risk. The low level of tibial baseplate migration found in the present study correlates to the low rate of revision for this implant as reported in individual studies and in joint replacement registries.

Aims

The purpose of the present study was to examine the long-term fixation of a cemented fixed-bearing polished titanium tibial baseplate (Genesis ll).